The present embodiments relate to ascertaining a fluid-dynamic characteristic value of a resilient vascular tree through which a fluid flows in a pulsating manner.
The vascular tree may be, for example, coronary arteries of a heart of a person or animal. Coronary heart disease is one of the most common and expensive disease patterns with a dramatic course. Stent implantation has proven itself as a treatment for coronary heart disease. Stent implantation is one of the most common therapies and is performed in the cardiac catheterization laboratory. In this way, constrictions (e.g., stenoses) may be widened or at least stabilized. The effect of a stenosis, and therewith the need for the stenosis to be treated, depends, however, not just on the extent of the constriction, but also on the size of the subsequent perfusion area. Similar degrees of stenosis may therefore necessitate different therapeutic treatment strategies. Treatment of a hemodynamically harmless stenosis is of no advantage to the patient, so treatment may be abstained owing to the risk of a stent implantation.
To be able to decide about a treatment, a hemodynamic characteristic value of the vascular tree constricted by the stenosis is to be ascertained. Various, supplementary examination methods that may provide information about the functional relevance of a stenosis have therefore been introduced. A hemodynamic characteristic value of this kind is the fractional flow reserve. The drop in pressure over the stenosis is ascertained in this connection using a pressure level measurement. In this method, the mean pressure is to be measured proximally and distally of the stenosis with maximum blood flow, and is to be related. If the value drops below a certain threshold value, a hemodynamically significant stenosis may be assumed. One drawback of this method is that the method is catheter based (e.g., is invasive). With maximum vasodilatation, something that may be achieved by administering adenosine, the measurement brings an additional burden for the patient.
It is known from U.S. Pat. No. 8,311,748 B2, U.S. Pat. No. 8,315,821 B2 and U.S. Pat. No. 8,321,152 B2 that a model of a vascular tree that is to be analyzed hemodynamically may be generated based on 3D image data of a computer tomograph (CT), a magnetic resonance tomograph (MRT), or a proton emission computer tomograph (PET), and may be carried out using the model computer-based fluid-dynamic calculations (Computational fluid Dynamics (CFD)). In a scientific study by Taylor et al. (Charles A. Taylor, Timothy A. Fonte, James K. Min, “Computational Fluid Dynamics Applied to Cardiac Computed Tomography for Noninvasive Quantification of Fractional Flow Reserve,” Journal of American College of Cardiology, published by Elsevier Inc, 2013) it was found, however, that, when generating such 3D image data using a computer tomograph, artifacts that affect the validity of a computer-based calculated FFR value are produced in the model of the vascular tree.
The reason for the artifacts is the aggravated recording condition that during execution of computer tomography blood flows through the examined vascular tree in a pulsating manner in time with the heartbeat, and the resilient walls of the vessels deform as a result.
An adaptive method for CFD calculation by which differences in a cardiovascular model from the underlying image data are compensated is known from U.S. Pat. No. 8,200,466 B2. In this method, the complexity of the cardiovascular model (e.g., the computing effort for this model) increases all the more, the more movement artifacts the underlying image material has.
In connection with cardiovascular models, a method for simulating an operation based on a model of this kind is known from U.S. Pat. No. 6,236,878 B1. The significance of a simulation of this kind depends on the quality of the model. The model is generated based on CT data or MR data in the document.